Fluid control valves are commonly distributed throughout process control systems to control flow rates and/or pressures of various fluids (e.g. liquids, gases, etc.). A fluid control valve is typically operatively connected to an actuator assembly to displace a valve stem to operate the fluid control valve. Typically, movement of the actuator moves the valve stem to position a plug or flow control member within the valve. In the case of a piston actuator, a pressure differential across a piston of the actuator displaces the piston, which in turn moves or rotates the valve stem to operate the valve. For example, the Fisher® 1061 pneumatic piston rotary actuator can be used to operate splined-shaft rotary control valves such as the Vee-Ball™ valves, eccentric disc valves, and butterfly valves. The actuator/valve body linkage of this actuator can be positioned for either push-down-to-open or push-down-to-close action.
In certain circumstances, it may be desirable to limit the travel of the piston within the actuator, which in turn will limit the movement of the valve. However, in typical piston actuators, this travel of the piston is limited using fixed travel stops within the cylinder of the actuator. Therefore, there is no way to adjust the travel limit of the piston without removing the cylinder of the piston actuator and either replacing the cylinder of piston actuator with a different cylinder having a different sized fixed travel stop or removing the currently installed fixed travel stops and replacing them with different sized fixed travel stops. Therefore, it would be desirable to have a piston actuator that had a travel stop that could be adjusted to various travel distances for the piston without having to disassembly the piston actuator.